The present invention relates to an acrylic acid-based star polymer and, more particularly, to a star polymer containing a repeating unit derived from a polyacrylate as a core portion and a repeating unit derived from an acrylic ester as an arm portion.
It has been known that a star polymer is obtained by polymerizing methyl methacrylate, isobutyl methacrylate and t-butyl methacrylate using, as an initiator, diphenylhexyllithium obtained by reacting 1,1-diphenylethylene with s-butyllithium, and reacting with dicumyl alcohol dimethacrylate or 2,5-dimethyl-2,5-hexanediol dimethacrylate (see, for example, Nonpatent Document 1).
[Nonpatent Document 1] L. Kilian, et. al., J. Polymer Science, Part A, 2003, 3083.